Tissue removal device for neurosurgical and spinal surgery applications

ABSTRACT

A tissue cutting device that is especially suited for neurosurgical applications is disclosed and described. The device includes a handpiece and an outer cannula in which a reciprocating inner cannula is disposed. The inner cannula includes a hinge between a body section and a cutting section that allows the cutting section to pivot when the inner cannula reciprocates within the outer cannula. A tissue collector is also provided and is in fluid communication with the lumen of the inner cannula. The inner cannula reciprocates at a rate that is greater than 1000 reciprocations per minute, and variable aspiration may also be provided to the device to control tissue traction and provide fine shaving and debulking.

TECHNICAL FIELD

The present disclosure relates to tissue cutting devices, in particular,tissue cutting devices that are suited for neurosurgical and spinalsurgical procedures.

BACKGROUND

Various abnormalities of the neurological system, such as brain andspinal tumors, cysts, lesions, or neural hematomas, can cause severehealth risks to patients afflicted by them, including deterioration inmotor skills, nausea or vomiting, memory or communication problems,behavioral changes, headaches, or seizures. In certain cases, resectionof abnormal tissue masses is required. However, given the complexity andimportance of the neurological system, such neurosurgical procedures areextremely delicate and must be executed with great precision and care.Many known tissue cutting devices suffer from an inability to quicklyand cleanly sever neurological tissue samples without causing “traction”or pull on the surrounding tissue. In addition, many known devices arenot configured to both “debulk” large structures and to finely shavesmaller, more delicate structures and lack the flexibility needed inmany procedures. Furthermore, many neurological procedures imposesignificant space limitations on the surgeon, and the tissue resectiondevice needs to be manipulable by the surgeon with one hand inrelatively small spaces. Many known devices either emulsify the resectedtissue, macerate the resected tissue, or thermally damage the tissuerendering it unsuitable for subsequent analysis (e.g., pathologic and/orhistologic analysis) which is necessary for the determination of themost effective post resection treatment therapies. Thus, a need hasarisen for a tissue cutting device that addresses the foregoing issues.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described by way ofexample in greater detail with reference to the attached figures, inwhich:

FIG. 1 is a perspective view of a tissue cutting device in accordancewith a first embodiment;

FIG. 2 is a cross-sectional view of the tissue cutting device of FIG. 1depicting an inner cannula in a first relative position with respect toan outer cannula in which the inner cannula's distal end is locatedproximally of the outer cannula's distal end;

FIG. 3 is a cross-sectional view of the tissue cutting device of FIG. 1depicting the inner cannula in a second relative position with respectto the outer cannula in which the inner cannula's distal end is locatedat the distal end of the outer cannula;

FIG. 4 is a partial cross-sectional view of the tissue cutting device ofFIG. 1 in a first configuration in which a device-mounted tissuecollector is disconnected from a tissue cutting device housing;

FIG. 5 is a partial cross-sectional view of the tissue cutting device ofFIG. 4 in a second configuration in which the device-mounted tissuecollector is connected to the tissue cutting device housing;

FIG. 6 is a partial cross-sectional view of an alternate embodiment ofthe tissue cutting device of FIG. 1 in a first configuration in whichthe device-mounted collector is disconnected from the tissue cuttingdevice;

FIG. 7 is partial cross-sectional view of the tissue cutting device ofFIG. 6 in a second configuration in which the device-mounted tissuecollector is connected to the tissue cutting device;

FIG. 8 is a broken side elevation view of the outer cannula of thetissue cutting device of FIG. 1;

FIG. 9 is a broken side elevation view of the inner cannula of thetissue cutting device of FIG. 1;

FIG. 10 is a top plan view of a portion of the outer cannula of thetissue cutting device of FIG. 1 with the inner cannula removed from theouter cannula;

FIG. 11 is a top plan view of a portion of the inner cannula of thetissue cutting device of FIG. 1;

FIG. 12 is a top plan view of a portion of the outer cannula and innercannula of FIG. 1 depicting the inner cannula inserted into the outercannula;

FIG. 13 is a partial cross-sectional view of a distal region of theouter cannula and the inner cannula of the tissue cutting device of FIG.1, depicting the inner cannula in a first relative position with respectto the outer cannula;

FIG. 14 is a partial cross-sectional view of a distal region of theouter cannula and the inner cannula of the tissue cutting device of FIG.1, depicting the inner cannula in a second relative position withrespect to the outer cannula;

FIG. 15 is an exploded assembly view of the tissue cutting device ofFIG. 1;

FIG. 16 a is a side elevation view of a cam of the tissue cutting deviceof FIG. 1;

FIG. 16 b is an end elevation view of the cam of FIG. 16 a;

FIG. 17 a is a perspective view of a cam transfer mechanism of thetissue cutting device of FIG. 1;

FIG. 17 b is a perspective view of a cam follower of the tissue cuttingdevice of FIG. 1;

FIG. 18 is a partial perspective view of a portion of the tissue cuttingdevice of FIG. 1 with an upper shell of an outer sleeve upper housingremoved to show a dial for rotating the outer cannula;

FIG. 19 is a partial side cross-sectional view of the portion of thetissue cutting device of FIG. 18;

FIG. 20 is a side elevation view of an inner and outer cannula assemblyof the tissue cutting device of FIG. 1;

FIG. 21A is a tissue cutting system including a remote tissue collector,control console, foot pedal, and the tissue cutting device of FIG. 1;

FIG. 21B is an enlarged view of the remote tissue collector of FIG. 21A;

FIG. 22 is a block diagram of a control scheme for the tissue cuttingsystem of FIG. 22;

FIG. 23 is diagram of the tissue cutting device of FIG. 1 and the motorcontrol unit of FIG. 22;

FIG. 24 is a partial cross-sectional view of the tissue cutting deviceof FIG. 1 depicting motor shaft position sensors for controlling a stopposition of an inner cannula;

FIG. 25 is a partial cross-sectional view of the outer cannula and innercannula of the tissue cutting device of FIG. 1 with the inner cannula ina first position relative to the outer cannula;

FIG. 26 is a partial cross-sectional view of the outer cannula and innercannula of the tissue cutting device of FIG. 1 with the inner cannula ina second position relative to the outer cannula; and

FIG. 27 is a partial cross-sectional view of the outer cannula and theinner cannula of the tissue cutting device of FIG. 1 with the innercannula in a third position relative to the outer cannula.

DETAILED DESCRIPTION

Referring now to the discussion that follows and also to the drawings,illustrative approaches to the disclosed systems and methods are shownin detail. Although the drawings represent some possible approaches, thedrawings are not necessarily to scale and certain features may beexaggerated, removed, or partially sectioned to better illustrate andexplain the present disclosure. Further, the descriptions set forthherein are not intended to be exhaustive or otherwise limit or restrictthe claims to the precise forms and configurations shown in the drawingsand disclosed in the following detailed description.

Described herein are tissue cutting devices that are suited forneurosurgical applications such as the removal of spine and braintissue. The devices are configured to provide high speed reciprocation,variable aspiration, and/or combinations of both high speedreciprocation and variable aspiration. As a result, the tissue cuttingdevices of the present disclosure provide surgeons with an enhancedability to vary and control the extent of tissue cutting as well as theimpact on surrounding tissue during tissue cutting procedures.

Referring to FIG. 1, a tissue cutting device 40 includes a handpiece 42and an outer cannula 44. In one exemplary configuration, handpiece 42 isgenerally cylindrical in shape and is preferably sized and shaped to begrasped with a single hand. Handpiece 42 includes a lower housing 50which comprises a proximal section 46 and distal section 48. Lowerhousing 50 comprises a proximal-most housing portion 82 (FIGS. 2 and 3)that is connected to a motor housing 71, and a cam housing 69 that isconnected to motor housing 71. A front housing section 51 is connectedto cam housing 69. Upper housing 42 is also provided. A tissue collector58 may be operatively connected to upper housing 52 (as will beexplained in further detail below). A rotation dial 60 for rotating theouter cannula 44 with respect to handpiece 50 is also mounted to upperhousing 52.

As best seen in FIGS. 2, 3, and 20, outer cannula 44 includes an openproximal end 45, a closed distal end 47, and a distal opening 49proximate distal end 47. Tissue cutting device 40 further comprises aninner cannula 76 which is partially disposed in an outer cannula lumen110. Inner cannula 76 is configured to reciprocate within outer cannulalumen 110 and to cut tissue samples entering outer cannula 44 via outercannula distal opening 49, as will be described in greater detail below.Inner cannula 76 reciprocates between a proximal position, which isdepicted in FIG. 2 and a distal position which is depicted in FIG. 3.Inner cannula 76 includes an open proximal end 77 and an open distal end79. Distal end 79 is preferably configured to cut tissue, and inpreferred embodiments is capable of cutting neurological system tissuessuch as those from the brain or spine. In one exemplary embodiment,inner cannula distal end 79 is beveled in a radially inward direction tocreate a sharp circular tip and facilitate tissue cutting.

Outer cannula 44 is not translatable, and its position with respect tohandpiece 42 along the direction of the longitudinal axis of handpiece42 remains fixed. Motor 62 is disposed in proximal lower housing section46 of handpiece 42 and is operably connected to inner cannula 76 todrive the reciprocation of inner cannula 76 within outer cannula lumen110. Motor 62 may be a reciprocating or rotary motor. In addition, itmay be electric or hydraulic. However, in the embodiment of FIGS. 2 and3, motor 62 is a rotary motor, the rotation of which causes innercannula 76 to reciprocate within outer cannula lumen 110.

Motor 62 is housed in motor housing 71, which defines a portion of lowerhousing proximal section 46. Motor 62 is connected to an inner cannuladrive assembly 63 which is used to convert the rotational motion ofmotor 62 into the translational motion of inner cannula 76. At itsproximal end, motor housing 71 is connected to proximal-most housingportion 82, which includes a power cable port 84 and a hose connector43, which in the exemplary embodiment of FIG. 3 is an eyelet. Hoseconnector 43 provides a means of securely retaining a vacuum system hoseto handpiece 42, thereby allowing vacuum to be supplied to tissuecollector 58.

Inner cannula driver assembly 63 (not separately shown in figures)comprises a cam 64, a cam follower 68, a cam transfer 72, and a cannulatransfer 74. Cam 64 is a generally cylindrical structure and is shown indetail in FIGS. 16A and 16B. A groove or channel 65 is defined in thesurface of cam 64. In one exemplary embodiment, groove 65 is continuousand circumscribes the perimeter of cam 64 but is not orientedperpendicularly to the longitudinal axis of cam 64, i.e., groove 65 isangled with respect to the cam axis. Opposing points on groove 65 suchas points 65 a and 65 b define pairs of “apexes” that are spaced apartalong the longitudinal axis of the cam, i.e., the groove extends along aportion of the length of the cam. Cam 64 also includes a proximalopening 114 (FIG. 16 a) for receiving a motor shaft and a proximalrecess 116 into which a shaft may be snugly received. Holes 118 and 120are provided for mounting position indicators that cooperate with aposition sensor to determine the angular position of cam 64, andcorrespondingly, the linear position of inner cannula 76 within theouter cannula lumen 110, as discussed below.

Cam follower 68 is depicted in detail in FIG. 17B. Cam follower 68 is agenerally rectangular block shaped structure with a hollow interior inwhich cam 64 is partially disposed. Cam follower 68 also includes a hole70 in its upper face in which a ball bearing (not shown) is seated. Theball bearing rides in cam groove 65 and engages cam transfer 72. As aresult, when cam 64 rotates, cam follower 68 translates along the lengthof handpiece 42. Cam follower 68 also includes lateral slots 182 a and182 b that cooperatively engage corresponding members 178 a, 178 b fromcam transfer 72.

Cam follower 68 is disposed within a cam chamber 67 formed in camhousing 69. Cam 64 is partially disposed in cam chamber 67 and extendsproximally therefrom to engage motor 62. Cam housing 69 comprises partof distal portion 48 of handpiece 42. Cam 64 does not reciprocate withincam chamber 67 and instead merely rotates about its own longitudinalaxis. However, cam follower 68 reciprocates within cam chamber 67 alongthe direction of the length of handpiece 42. Cam follower 68 is open atits proximal end to receive cam 64. As shown in FIGS. 15 and 16A, cam 64may optionally include a threaded distal end 123 that projects through adistal opening 191 (FIG. 17 b) in cam follower 68 and which engages anut 190 (FIG. 15) to prevent reciprocation of cam 64 relative to camhousing 69. Proximal cam bearing 186 and distal cam bearing 188 (FIG.15) may also be provided to support cam 64 as it rotates within camhousing 69.

Cam transfer 72 extends from cam chamber 67 into a cam transfer chamber73 formed in upper housing 52. As best seen in FIG. 17 a, cam transfer72 comprises a proximal end 72 a that is attachable to cam follower 68and a distal end 72 b that is attachable to inner cannula 76 via cannulatransfer 74. Proximal end 72 a comprises a pair of spaced apart,downwardly extending members 178 a and 178 b, and distal end 72 bcomprises a pair of spaced apart upwardly extending members 180 a and180 b. Downwardly extending members 178 a and 178 b are spaced apart ina direction that is perpendicular to the length of cam 64 and handpiece42, while upwardly extending members 180 a and 180 b are spaced apart ina direction that is parallel to the length of cam 64 and handpiece 42.Cam follower slots 182 a and 182 b engage downwardly extending members178 a and 178 b of cam transfer 72. Downwardly extending members 178 aand 178 b of cam transfer 72 may be resilient and may have engagementportions 179 a and 179 b on their free ends (e.g., hooks or clips) forsecurely engaging the bottom and side surfaces of cam follower 68.

As best seen in FIG. 20, cannula transfer 74 comprises a sleeve disposedabout inner cannula 76. Cannula transfer 74 comprises a proximal end128, middle section 127, and distal end 126. Upwardly extending members180 a and 180 b of cam transfer 72 define fork-shaped structures thatreceive and cradle middle section 127 of cannula transfer 74. Distal end126 and proximal end 128 of cannula transfer 74 are disposed outwardlyof upwardly extending members 180 a and 180 b and are shaped to preventrelative translation between cam transfer 72 and cannula transfer 74. Inthe depicted embodiments, distal end 126 and proximal end 128 of cannulatransfer 74 are enlarged relative to middle section 127 to abut theupwardly extending, fork-shaped members 182 a and 182 b, therebypreventing relative translation between cam transfer 72 and cannulatransfer 74. As a result, when cam transfer 72 reciprocates along thelength of handpiece 42, cannula transfer 74 reciprocates as well.Because it is affixed to inner cannula 76, when cannula transfer 74reciprocates, it causes inner cannula 76 to reciprocate within outercannula 44.

In one exemplary arrangement, motor 62 is a brushed DC motor and may beoperably connected to cam 64 in a number of ways. In the embodiment ofFIGS. 2 and 3, motor 62 includes a distally extending shaft 66 thatextends into a proximal opening 114 and engages recess 116 defined incam 64. Shaft 66 may be connected to cam 64 via a threaded connection,adhesive, or other known connection means. In an alternateimplementation, depicted in FIG. 15, a separate cam coupler 184 isprovided. Cam coupler 184 is seated in proximal opening 114 and has awidth greater than the diameter of opening 114. Cam coupler 184 is alsoconnected to motor shaft 66 such that rotation of shaft 66 causes camcoupler 184 to rotate, which in turn causes cam 64 to rotate therewith.One revolution of motor shaft 66 causes cam 64 to rotate by onerevolution, which in turn causes inner cannula 76 to reciprocate by onecomplete stroke, i.e., from the position of FIG. 2 to the position ofFIG. 3 and back to the position of FIG. 2.

Cam transfer 72 may be connected to cam follower 68 by mechanical means,adhesive means or other known connection means. In one exemplaryembodiment, downwardly extending members 178 a and 178 b mechanicallyclip onto and removably engage cam follower 68. In another embodiment,cam transfer 72 is adhesively affixed to cam follower 68. In yet anotherembodiment, both mechanical and adhesive connections are used. The ballbearing (not shown) disposed in cam follower hole 70 traverses camgroove 65 as cam 64 rotates, causing cam follower 72 to reciprocate fromthe proximal position of FIG. 2 to the distal position of FIG. 3. As aresult, cam transfer 72, cannula transfer 74 and inner cannula 76translate between their respective proximal positions of FIG. 2 andtheir respective distal positions of FIG. 3 when motor 62 and cam 64rotate. In certain examples (not separately shown), motor 62 may beconnected to a cam follower, and the cam follower may be connected to acam which is in turn operatively connected to the inner cannula. Inaccordance with these examples, when the motor rotates, the cam followerrotates and causes the cam to reciprocate, thereby causing the innercannula to reciprocate.

Motor 62 is preferably selected to have a rotational speed that allowsinner cannula 76 to reciprocate from the position of FIG. 2 to theposition of FIG. 3 and back to the position of FIG. 2 at a rate of atleast about 1,000 reciprocations/minute. Reciprocation rates of at leastabout 1,200 reciprocations/minute are more preferred, and reciprocationrates of at least about 1,500 reciprocations/minute are even morepreferred. Reciprocation rates of less than about 2,500reciprocations/minute are preferred. Reciprocation rates of less thanabout 2,000 are more preferred, and reciprocation rates of less thanabout 1,800 reciprocations/minute are even more preferred. As best seenin FIG. 14, the rates of reciprocation of device 40 allow tissue to besevered into “snippets” 112 which are relatively smaller than “slug”tissue samples obtained by many prior devices. As the reciprocationcontinues, a continuum of severed tissue snippets 112 is obtained.

As mentioned previously, outer cannula 44 includes an opening 49 forreceiving tissue into outer cannula lumen 110. As best seen in FIGS.8-12, opening 49 is preferably defined by a cutting edge 51 that isconfigured to sever tissue and a non-cutting edge 53 that is notconfigured to sever tissue. In certain exemplary implementations,cutting edge 53 has a radial depth “d” that is no greater than about 50%of the outer diameter of outer cannula 44. In one exemplaryimplementation, cutting edge 51 is beveled in a radially inwarddirection, non-cutting edge 53 is not beveled, and cutting edge 51 islocated immediately distally of non-cutting edge 53. Inner cannuladistal end 79 is preferably configured to cut tissue. In one exemplaryembodiment, distal end 79 is beveled in a radially inward directionaround the circumference of inner cannula 76 to provide a sharp edge. Astissue is received in outer cannula opening 49, it is compressed betweeninner cannula distal end 79 and outer cannula cutting edge 51, causingthe received tissue to be severed from the surrounding tissue.

Tissue cutting device 40 is particularly well suited for use in cuttingtough tissues such as spinal and brain tissues. Outer cannula 44 andinner cannula 76 comprise materials that are generally rigid, such asrigid plastics or metal. In one preferred implementation, both cannulaecomprise stainless steel, and more preferably, 304SS typically used inmedical grade instruments.

As best seen in FIGS. 9-13, to facilitate the cutting of tough tissues,inner cannula 76 includes a hinge 80. Hinge 80 is located between innercannula body section 81 which is located on the proximal side of hinge80 and inner cannula cutting section 83 which is located on the distalside of hinge 80. In one exemplary arrangement, hinge 80 is a livinghinge. As used herein, the term “living hinge” refers to a thin,flexible hinge that joins two relatively more rigid parts together. Inone example, hinge 80 is a living hinge that is integrally formed withinner cannula body section 81 and inner cannula section 83 by removing aportion of the circumference of the inner cannula 76 along a length L(FIG. 11). Hinge 80 allows cutting section 83 to pivot about hinge 80 asinner cannula 76 reciprocates within outer cannula 44. As inner cannula76 translates in the distal direction, it contacts tissue received inouter cannula opening 49 and encounters progressively increasingresistance from the tissue as the tissue is urged in the distaldirection. As the resisting force of the tissue increases, cuttingsection 83 pivots progressively more until a zero annular clearance isobtained between inner cannula distal end 79 and outer cannula opening49. The received tissue is severed and aspirated in the proximaldirection along inner cannula lumen 110 and received in tissue collector58. Thus, inner cannula lumen 110 provides an aspiration path from theinner cannula distal end 79 to the inner cannula proximal end 77. Hinge80 allows a generally zero annular clearance to be obtained betweeninner cannula distal end 79 and outer cannula opening 49 at cuttingsection 80 while not affecting the annular clearance between innercannula body section 81 and outer cannula 44. This configurationmaximizes tissue cutting while minimizing frictional losses that wouldotherwise occur due to the frictional engagement of the outer surface ofinner cannula body section 81 and the inner surface of outer cannula 44if a very small annular clearance between the outer cannula 44 and innercannula 76 were present.

Outer cannula opening 49 may have a number of shapes. In certainexamples, when outer cannula opening 49 is viewed in plan, it has ashape that is generally square, rectangular, trapezoidal, ovular, or inthe shape of the letter “D.” In certain other exemplary implementations,outer cannula opening 49 is configured to direct tissue so that it maybe compressed as inner cannula 76 translates in the distal direction. Inone such implementation, depicted in FIGS. 10 and 12, outer cannulaopening 49 has a generally triangular shape when outer cannula opening49 is viewed in plan. As FIGS. 10 and 12 indicate, when viewed in plan,the width of opening 49 in a direction transverse to the outer cannulalongitudinal axis varies longitudinally along the length of outercannula 44, and preferably narrows from the proximal to distal portionsof opening 49. When viewed in side elevation, cutting edge 51 slopes ina radially outward direction moving distally along edge 51. As a result,as a tissue sample is distally urged within outer cannula opening 49 bythe action of inner cannula 76, the tissue is increasingly compressed inthe direction of the circumference of inner cannula 76 (or in thedirection of the “width” of opening 49 when viewed in plan). To ensurecomplete cutting, inner cannula distal end 79 preferably travels to aposition that is distal of outer cannula opening 49 during a tissuecutting operation, i.e., there is an inner cannula overstroke.

As mentioned above, tissue cutting device 40 aspirates tissue samplesreceived in inner cannula lumen 78 to cause the tissue samples to movein the proximal direction along the length of the inner cannula 76. Incertain methods of use, device 40 is used to resect tissue withoutcollecting tissue samples for further analysis. In such embodiments, atissue collector need not be provided. In other embodiments whereintissue collection is desired, device 40 preferably includes a tissuecollector 58 into which aspirated tissue samples are deposited during atissue cutting procedure. Tissue collector 58 may be located remotelyfrom handpiece 42 and outside the sterile field during a tissue cuttingoperation as shown in FIG. 21A. However, in an alternative embodiment,as best seen in the examples of FIGS. 1-7, tissue collector 58 isremovably connected to handpiece 40. In either embodiment, a fluidcollection canister 192 is preferably located between tissue collector58 and a source of vacuum (such as vacuum generator 153 in FIG. 21A) toprotect the vacuum generating apparatus from becoming contaminated ordamaged by aspirated fluids. In those embodiments that lack a tissuecollector, fluid collection canister 192 may be provided to collect bothaspirated fluid and tissue.

Referring to FIGS. 4-7, tissue collector 58 is connected to upperhousing 52 proximally of the inner cannula 76 to receive the aspiratedtissue samples. Tissue collector 58 is a generally cylindrical, hollowbody with an interior volume that is in fluid communication with theinner cannula lumen 78 and a source of vacuum (not shown in FIGS. 4-7).Tissue collector 58 is removably secured to housing connector 96 toallow for the periodic removal of collected tissue samples. Tissuecollector 58 is preferably secured to upper housing 52 in a manner thatprovides a substantially leak-proof vacuum seal to maintain consistentaspiration of severed tissue samples. A vacuum hose fitting 59 is formedon the proximal end of tissue collector 58 and is in fluid communicationwith the interior of tissue collector 58 and with a vacuum generator, aswill be discussed below.

In the embodiment of FIGS. 4-5, housing connector 96 is a generallycylindrical, flange extending proximally from upper housing 52. Uppershell 54 and lower shell 56 of upper housing 52 cooperatively define acavity into which a seal holder 94 is partially disposed. Seal holder 94includes a distal annular recess in which a seal 92, such as an o-ring,is disposed. Seal holder 94 also includes a central lumen through whichinner cannula 76 is slidably disposed. A proximally projecting portion95 of seal holder 94 projects away from upper housing 52 in the proximaldirection and is received within housing connector 96. As best seen inFIGS. 2 and 3, inner cannula proximal end 77 preferably remains withinseal holder 94 as inner cannula 76 reciprocates during operation oftissue cutting device 40. However, proximal end 77 moves within sealholder 94 as inner cannula 76 reciprocates. Seal 92 preferably comprisesa resilient material such as an elastomeric material. The sealingengagement of seal 92 and inner cannula 76 prevents air or fluids fromleaking between inner cannula 76 and upper housing 52 and aids inmaintaining consistent aspiration of samples through the inner cannulalumen 78.

Housing connector 96 includes connecting features 98 and 100 which areconfigured to engage with corresponding connecting features 102 and 104on tissue collector 58. In the embodiment of FIGS. 4 and 5, connectingfeatures 98 and 100 are “J” shaped slots formed in housing connector 96,and connecting features 102 and 104 are complementary protrusions formedon tissue collector 58 which engage connecting features 98 and 100,respectively. To connect tissue collector 58 to housing connector 96,protrusions 102 and 104 are aligned with slots 98 and 100, and tissuecollector 58 is then inserted into housing connector 96 in the distaldirection. Tissue collector 58 is then rotated to fully engageprotrusions 102 and 104 with slots 98 and 100. A seal 103 is providedaround the circumference of tissue collector 58 to sealingly engage theinner surface of housing connector 96.

An alternate embodiment of tissue collector 58 is depicted in FIGS. 6and 7. In the embodiment of FIGS. 6 and 7, tissue collector 58 issemi-elliptical in cross-section and includes a hollow interior forreceiving samples, as in the embodiment of FIGS. 4 and 5. In theembodiment of FIGS. 6 and 7, a cylindrical flange housing connector 96is not provided. Instead, upper housing 52 is formed with an engagementrecess 108 that engages a complementary clip 106 formed on tissuecollector 58. In each of the foregoing embodiments, tissue collector 58may be provided with a filter (not shown) in its interior for collectingsolid tissue samples while allowing liquids and gases (e.g., air) topass through. Exemplary filters include medical grade mesh filters witha mesh size smaller than that of tissue snippets 112.

In the embodiments of FIGS. 4-7, tissue collector 58 preferably has alongitudinal axis that is not collinear with the longitudinal axes ofhandpiece 42, motor 62, and cam 64. The longitudinal axis of tissuecollector 58 is preferably substantially coaxial with the longitudinalaxis of inner cannula 76 to yield an “in-line” filter configuration.Tissue collector 58 and inner cannula 76 are both spaced apart from andsubstantially parallel to the longitudinal axes of handpiece 42, motor62, and cam 64. Thus, the cutting axis (i.e., the outer cannulalongitudinal axis) and sample aspiration path axis are not coaxial withthe longitudinal axis of the handpiece 42. As a result, when device 40is used to cut tissue, the surgeon's view of the cutting axis is notobstructed by his or her hand. In addition, the surgeon can treat theproximal end of the filter as a “gun sight” and align it with a tissuesample to be cut to thereby align the outer cannula 44 with the tissuesample, providing enhanced ergonomic benefits over previous devices, inparticular, previous neurosurgical devices. In the case of a device witha remote tissue collector 58 such as the one depicted in FIGS. 21A and21B, the user can treat the proximal end of upper housing 52 as a gunsight and align it with a target tissue.

When device 40 is used to cut tissue, outer cannula opening 49 must bealigned with the target tissue of interest to receive it for cutting.The entire device 40 can be rotated about the longitudinal axis ofhandpiece 42 to place outer cannula opening 49 at the desired location.However, this technique can be awkward and may reduce the surgeon'sdexterity. Thus, in an exemplary embodiment, device 40 includes aselectively rotatable outer cannula 44. As best seen in FIGS. 18-20, arotation dial 60 is provided and is rotatably seated in a cavity definedby upper shell 54 and lower shell 56 of upper housing 52. Rotation dial60 is configured such that when it is rotated, it causes outer cannula44 to rotate about its longitudinal axis. Rotation dial 60 is preferablyconnected to an outer cannula connector portion 88. In the embodiment ofFIGS. 18-20, outer cannula connector portion 88 is a sleeve that isintegrally formed with rotation dial 60 and which is fixedly secured toouter cannula 44 such as by an adhesive or other known connection means.In the exemplary embodiment of FIG. 20 rotation dial 60 has an outerdiameter that is greater than that of sleeve 88.

As mentioned previously, inner cannula 76 includes a hinge 80 to allowinner cannula cutting section 83 to pivot toward outer cannula opening49 when device 40 is in operation. In order to ensure the correctoperation of hinge 80, the circumferential alignment of hinge 80 andouter cannula opening 49 should be maintained. Thus, rotation dial 60 ispreferably connected to inner cannula 76 such that when rotation dial 60is rotated, both outer cannula 47 and inner cannula 76 rotate in a fixedangular orientation with respect to one another by an amount thatdirectly corresponds to the amount by which rotation dial 60 is rotated.Rotation dial 60 may be directly connected to inner cannula 76 or mayuse an intervening connecting device. However, rotation dial 60 shouldbe configured to allow inner cannula 76 to reciprocate with respect torotation dial 60. As best seen in FIG. 20, rotation dial inner cannulaconnector 86 may be provided to connect rotation dial 60 to innercannula 76. Rotation dial inner cannula connector 86 comprises aproximal sleeve 87 disposed about inner cannula 76 and a distal,radially extending annular flange 90 with an outer diameter greater thanthat of the sleeve 87. Sleeve 87 and flange 90 may be in the shape ofcircular cylinders. Alternatively, and as shown in FIGS. 18-19, sleeve87 and flange 90 may be in the shape of a polygonal cylinder. Sleeve 87is slidably received within the annular cavity 130 at the distal end 126of the cannula transfer 74 and keyed to the inner surface of cannulatransfer 74 at annular cavity 130 such that sleeve 87 can reciprocatewith respect to cannula transfer 74 while causing cannula transfer 74 torotate with sleeve 87 when rotation dial 60 is rotated. When innercannula 76 is reciprocated, cannula transfer distal end 126 reciprocateswith respect to sleeve 87, thereby variably adjusting gap “G” definedwithin annular cavity 130 (FIG. 20). Alternatively, cannula transferdistal end 126 may be slidably received in an annular cavity formed insleeve 87 and may be keyed to the inner surface of the annular cavity sothat cannula transfer may reciprocate with respect to sleeve 87 whilestill rotating with sleeve 87 when dial 60 is rotates.

As best seen in FIG. 20, rotation dial 60 includes a first annularcavity 61 that is sized to receive and engage flange 90 in a closefitting relationship. Rotation dial 60 may be press fit to flange 90. Inaddition, adhesive connections or mechanical connections may be used.Because rotation dial 60 is directly or indirectly connected to bothouter cannula 44 and inner cannula 76, both cannulae rotate in directcorrespondence to the rotation of rotation dial 60, thereby allowing theuser to adjust the orientation of outer cannula opening 49 and innercannula hinge 80 in a circumferential direction with respect tohandpiece 42. As a result, surgeons need not rotate the entire tissuecutting device 40 to obtain the desired angular orientation.

Rotation dial 60, outer cannula 44, and inner cannula 76 are preferablyconfigured for 360° rotation. In addition, tactile indicators arepreferably provided on rotation dial 60 to allow a user to reliablydetermine the extent to which dial 60 has been rotated from a givenstarting point. The tactile indication may comprise surface featuresdefined on or in the exterior surface of rotation dial 60. In oneexemplary embodiment, depicted in FIGS. 18-20, a plurality of ridges 122is provided around the circumference of rotation dial 60 to providetactile indication. The ridges also act as grips and facilitate thesurgeon's ability to rotate the dial 60 without transferring unwantedmotion to the surgical site.

As mentioned previously, vacuum (sub-atmospheric pressure) is applied totissue collector 58 to aspirate severed tissue samples through innercannula 76 in the proximal direction. The application of vacuum to innercannula 76 via tissue collector vacuum hose fitting 59 will have apropensity to produce a vacuum at proximal end 45 of outer cannula 44 ifleakage occurs between inner cannula 76 and the components of upperhousing 52. The generation of a vacuum at outer cannula proximal end 45will in turn cause fluids and/or tissue samples at the distal end ofouter cannula 44 to flow into the annular clearance between innercannula 76 and outer cannula 44 that extends from its proximal end atouter cannula proximal end 45 to its distal end at inner cannula distalend 79. This fluid and/or tissue can result in blockage of the annularclearance and increased friction between the inner cannula 76 and outercannula 44, resulting in degraded performance. Accordingly, a seal 129is preferably provided to prevent air artifacts, fluid (water, saline,blood, etc.) flow, and tissue sample flow in the annular clearancebetween inner cannula 76 and outer cannula 44. The seal 129 ispreferably disposed adjacent the proximal end of the annular clearancebetween inner cannula 76 and outer cannula 44, i.e., proximally adjacentto outer cannula proximal end 45. As shown in FIG. 20, seal 129 ispreferably annular and circumscribes inner cannula 76, extending fromthe outer surface of inner cannula 76 in a radially outward direction aswell as longitudinally along a portion of the length of inner cannula76.

In the embodiment of FIG. 20, rotation dial 60 and sleeve 87 act as aseal housing and include a seal cavity 131 which is an annular cavitydisposed immediately adjacent to and distal of first annular cavity 61.Seal cavity 131 is sized to accept seal 129 therein. The seal 129 may bea conventional seal such as a solid, flexible and/or elastomeric o-ring.However, seal 129 is preferably amorphous and comprises a thixotropicmaterial that is a semi-solid. It is further preferred that seal 129fill the entirety of seal cavity 131 to ensure that cavity 131 issubstantially leak free. In the exemplary embodiment of FIG. 20, sealcavity 131 has an outer diameter that is greater than the outer diameterof outer cannula 44. Moreover, the annular thickness of seal cavity 131is preferably greater than the annular clearance between outer cannula45 and inner cannula 76 to better ensure complete sealing of the annularclearance.

In one exemplary embodiment, seal 129 is a grease—such as the so-called“high vacuum greases”—that is formulated to withstand vacuum conditions.Suitable high vacuum greases include halogenated polymers. Thehalogenated polymers are preferably based on cyclic ethers orunsaturated hydrocarbon polymeric precursors. In one exemplaryembodiment, a perfluroropolyether (PFPE) grease is used. Examples ofsuch greases include the FOMBLIN® family of greases supplied by SolvaySolexis, Inc. Other examples of such greases includepolytetrafluroroethylene greases (“PTFE”) such as TEFLON® greasessupplied by DuPont. One suitable high vacuum grease is FOMBLIN® Y VAC3grease, which is a PFPE grease with a PTFE thickener. The semi-solidseal 129 preferably has a kinematic viscosity at 20° C. of at leastabout 500 cSt, more preferably at least about 800 cSt, and even morepreferably at least about 1200 cSt. Semi-solid seal 129 preferably has akinematic viscosity at 20° C. of no greater than about 2500 cSt, morepreferably no greater than about 2000 cSt, and even more preferably nogreater than about 1700 cSt.

The use of a semi-solid seal 129 has several advantages. Because theseal is semi-solid, it will tend to absorb and dampen vibrationstransmitted from the reciprocation of the inner cannula, therebyreducing overall vibration of device 40, and in particular, thevibration transmitted to outer cannula 44. The dampening of suchvibrations is particularly beneficial because it prevents unwantedvibration of outer cannula 44 which can disturb delicate neurosurgicalprocedures. Moreover, because it is not a solid seal, seal 129 willexperience less heating and wear as it is frictionally engaged by thereciprocating inner cannula 76. In certain embodiments, a portion ofseal 129 will adhere to the outer surface of inner cannula 76 as itreciprocates producing a zero slip velocity condition at the innercannula 76 outer surface which may further reduce frictional heating anddegradation of seal 129. Because semi-solid seal 129 produces lessfrictional resistance to the reciprocation of inner cannula 76 ascompared to conventional solid seals such as o-rings, it also decreasesthe required motor power consumption and can facilitate the use of lowertorque and lower cost motors, which in turn facilitates making device 40disposable.

In one configuration, device 40 is connected to a vacuum source andconfigured for variable aspiration, i.e., configured to supply variablelevels of vacuum to inner cannula lumen 78. As depicted in FIG. 21A, inone exemplary implementation, a tissue cutting system is provided whichcomprises tissue cutting device 40, a tissue collector 58, a controller132, a vacuum generator 153, a vacuum actuator 144, a controllable valve146, a vacuum line 151, and a fluid collection canister 192. Asmentioned previously, in FIG. 21A tissue collector 58 is locatedremotely from handpiece 42 and may be placed far enough from thehandpiece 42 to remain outside of the sterile field during a tissuecutting operation. As best seen in FIG. 21B, tissue collector 58 isgenerally the same as the tissue collector 58 depicted in FIGS. 4-5.Vacuum line 151 a connects the distal end of tissue collector 58 toproximally projecting portion 95 of seal holder 94 on the proximal endof tissue cutting device upper housing 52. In one arrangement, theproximal end of vacuum line 15 la includes a hose fitting 59 b that isintegrally formed with a tissue collector coupler 296. Coupler 296 issimilar in structure to tissue collector connector 96 (FIGS. 4-5) and isa cylindrical structure with a hollow interior for receiving a portionof tissue collector 58. As best seen in FIG. 21B, tissue collector 58includes projections 202 and 204 which engage complementary slots 298and 200 in coupler 296 in the same manner that projections 102 and 104engage slots 98 and 100 in FIGS. 4-5. At the proximal end of tissuecollector 58, hose fitting 59 a engages vacuum line 151 b which in turnis connected to fluid collection canister 192. Fluid collection canister192 is connected to vacuum generator 153 via vacuum line 151 c. Vacuumgenerator 153 is connected to controllable valve 146 by way of pressureline 147.

The outlet of tissue collection canister 192 is preferably substantiallyliquid free and is connected to vacuum generator 153 via vacuum line 151c. Thus, vacuum generator 153 is in fluid communication with tissuecollector 58 and inner cannula lumen 78, thereby generating a vacuum atthe proximal end 77 of inner cannula 76 to aspirate severed tissuesamples from inner cannula distal end 79 to tissue collector 58. Thelevel of vacuum generated by vacuum generator is preferably variable andselectively controllable by a user. Maximum vacuum levels of at leastabout 0 in Hg. are preferred, and maximum vacuum levels of at leastabout 1 in Hg. are more preferred. Maximum vacuum levels of at leastabout 5 in Hg. are even more preferred, and maximum vacuum levels of atleast about 10 in Hg. are still more preferred. Maximum vacuum levels ofat least about 20 in. Hg. are yet more preferred, and vacuum levels ofat least about 29 in. Hg. are most preferred.

The controllable valve 146 and the vacuum generator 153 provide a meansfor continuously adjusting and controlling the level of vacuum appliedto tissue collector 58 and the proximal end of inner cannula lumen 78.Controllable valve 146 is supplied with a pressurized gas, preferablyair, or an inert gas such as nitrogen. In one exemplary embodiment, thepressure applied to controllable valve 146 is about 70 psi.

The system further includes an electrical controller 132 which receivesand provides signals to the various components to control or monitortheir operations. Controller 132 provides control signals to device 40via motor drive control line 142 to activate or deactivate motor 62. Anaspiration valve control line 150 extends from the controller 132 to thecontrollable valve 146 which provides pressure to the vacuum generator153. Signals to the controllable valve 146 through line 150 are used tocontrol the amount of vacuum applied to tissue collector 58.

Controller 132 also receives electrical signals from the variouscomponents of the system. For instance, a pressure transducer 148associated with the aspiration controllable valve 146, sends a signalalong line 152 to the controller 132. The signal is representative ofthe pressure supplied through controllable valve 146 to vacuum generator153. Thus, the transducer 148 provides immediate feedback to thecontroller which can in turn provide signals to aspiration controllablevalve 146.

The user can adjust the system operating parameters by using panelcontrols such as a console knob 138 and/or one or more depressiblecontrollers, such as a foot pedal 144. In one embodiment, foot pedal 144can be used to activate the motor 62 in device 40, causing the innercannula 76 to reciprocate within the outer cannula 44. In anotherembodiment, foot pedal 144 can be used to control the vacuum levelsupplied from vacuum generator 153 to tissue collector 58 and innercannula lumen 78. In another embodiment, foot pedal 144 can be used bothto activate motor 62 and to control the vacuum level supplied fromvacuum generator 153 to tissue collector 58. In one arrangement footpedal 144 is configured to variably increase the level of vacuum appliedto tissue collector 58 from a minimum level to a maximum level as footpedal 144 is depressed from a first position to a second position. Insuch an arrangement, the first position is one in which foot pedal 144is not depressed all or is only slightly depressed, and the secondposition is one in which foot pedal 144 is fully depressed. In anotherembodiment, knob 138 is used to set a preselected maximum vacuum levelapplied by vacuum generator 153. Thus, by depressing foot pedal 144 froma first fully open position to a second fully closed position, aplurality (preferably a continuum) of vacuum levels can be supplied totissue collector 58 with the maximum vacuum level being user adjustablevia knob 138.

In one exemplary embodiment, foot pedal 144 includes two switches (notshown) for providing variable vacuum and activating motor 62. In oneexemplary embodiment, once foot pedal 144 is partially depressed from anopen or undepressed position, motor 62 is activated. In accordance withthe embodiment, continued depression of foot pedal 144 activates vacuumgenerator 153. Foot pedal 144 preferably provides continuous movementbetween a fully open and a fully depressed position which in turncorresponds to a plurality, and preferably a continuum, of vacuum levelsthat are supplied to inner cannula lumen 78. Once foot pedal 144 isfully depressed, the vacuum level supplied to inner cannula lumen 78corresponds to a previously selected maximum vacuum level.

In certain illustrative examples, the user will adjust the level ofvacuum to achieve a desired level of “traction” in the tissuesurrounding the tissue to be severed. As used here in, the term“traction” refers to the exertion of a pulling force on tissuesurrounding the target tissue to be severed. In some instances, tractionmay be visualizable by the surgeon with the use of a magnificationinstrument, such as a microscope or an endoscope. The level of vacuumwill also determine the amount of unsevered tissue that is drawn intoouter cannula opening 49, and therefore, the size of the severed tissuesnippets 112 (FIG. 14). Therefore, when fine shaving operations aredesired, the vacuum level will be a relatively lower level than ifdebulking (large scale tissue removal) is performed. Of course, thepre-selected maximum vacuum level will also affect the maximum size oftissue that is drawn into outer cannula opening 49, and therefore, willaffect the maximum size of severed tissue samples during any oneoperation. Also, the vacuum level may be adjusted based on theelasticity, fibrotic content, and hardness/softness of the tissue.

Console 132 may also include indicator lights 136, one of whichindicates the activation of cutting and one of which indicates theactivation of aspiration. Console 132 may further include an analogdisplay 140 with readouts for “aspiration” and “cutter.” The“aspiration” read out indicates the vacuum level supplied to tissuecollector 58 from vacuum generator 153. The “cutter” read out indicatesthe speed of reciprocation of inner cannula 76. In one embodiment, aspeed sensor is mounted in device 40 to determine the speed ofreciprocation of inner cannula 76 and the sensor is input to controller132.

As mentioned previously, when device 40 is used to perform a cuttingoperation, inner cannula 76 reciprocates within outer cannula opening 49to sever tissue received within outer cannula opening 49. When a cuttingoperation is complete, it may be preferred to have inner cannula 76 cometo rest at a position that is proximal of the proximal edge 53 of outercannula opening 49 to ensure that tissue is not trapped between innercannula distal end 79 and outer cannula cutting edge 51. However, incertain methods of use, tissue cutting device 40 may be used as anaspiration wand without cutting any tissue. In these embodiments, thestop position of the inner cannula distal end 79 within outer cannulaopening 49 determines the open area of the outer cannula 44, andtherefore, the aspiration levels that can be applied immediatelyadjacent outer cannula opening 49. Thus, in some preferred embodiments,the inner cannula stop position is user adjustable. Tissue cuttingdevice 40 may be used to aspirate a variety of fluids associated with aneurosurgical procedure, including without limitation blood, saline,cerebrospinal fluid, and lactate ringer's solution. In certain examples,the inner cannula stop position is adjusted to provide a desired degreeof aspiration, outer cannula 44 is positioned proximate a target tissue,and vacuum is applied to manipulate the target tissue and draw it intoouter cannula opening 49. Outer cannula 44 is then moved to a desiredlocation or orientation, thereby moving the target tissue to the desiredlocation or orientation. Once the target tissue has been satisfactorilymanipulated, a cutting operation is initiated. By using device 40 inthis manner, target tissues can be drawn away from areas where tissuecutting operations are undesirable, and the cutting can be performedremotely from those areas.

In one exemplary system, an inner cannula position control is providedwhich controls the rest position of inner cannula 76 when motor 62 isdeactivated. Referring to FIG. 24, cam rotational position indicators176 a and 176 b are mounted on the proximal end of cam 62. In anexemplary embodiment, cam rotational position indicators 176 a and 176 bare magnets having opposite poles. A position sensor 174 is mounted onthe inner surface of cam housing 69 and generates a signal indicative ofthe rotational position of indicators 176 a and 176 b relative toposition sensor 174. As mentioned previously, the rotation of cam 62correlates directly to the position of inner cannula 76 within outercannula 44. Thus, the rotation of cam 62 can be sensed to indirectlydetermine the position of inner cannula 76. Accordingly, indicators 176a/176 b and sensor 174 can be used to determine the position of innercannula 76 with respect to proximal edge 53 of outer cannula opening 49(FIGS. 10-12).

Referring to FIG. 22, an embodiment of a system for controlling theoperation of tissue cutting device 40 is provided. The system includes amain control unit 158 (“MCU”), which (in the embodiment shown) isconfigured as a microprocessor-based system. In one implementation, MCU158 is incorporated in controller 132 (FIG. 21A) and is operable tocontrol the various operations of the tissue cutting device 40. Footswitch 144 is electrically connected to a number of inputs of MCU 158via an equal number, K, of signal paths 156, wherein K may be anyinteger. Panel controls, such as knob 138, are electrically connected toa number of inputs of MCU 158 via an equal number, J, of signal paths145, wherein J may be any integer.

Display unit 140 is electrically connected to a number of outputs of MCU158 via an equal number, Q, of signal paths 141, wherein Q may be anyinteger. In one exemplary implementation, depicted in FIG. 21A, displayunit 140 is provided on console 134.

As mentioned previously, tissue cutting device 40 includes motor 62coupled to the inner cannula 76 by an inner cannula drive assembly 63.The motor 62 is electrically connected to motor control unit 160 via anumber, M, of signal paths 161 wherein M may be any integer. The motorcontrol unit 160 is, in turn, connected to a number of outputs of MCU158 via an equal number, N, of signal paths 161. Cam rotational positionsensor 174 is electrically connected to a motor shaft position feedbackinput (SPF) of MCU 158 via signal path 162, and provides a motor stopidentification signal thereon as will be more fully describedhereinafter. The motor shaft stop identification signal provided bysensor 174 on signal path 162 preferably provides MCU 158 with a motorstop identification signal and may optionally provide a cutter speedsignal that is proportional to the motor speed for a geared system oridentical to the motor speed for a direct drive system.

Handpiece 40 is further mechanically connected to a vacuum unit 168(e.g., a combination of controllable valve 146 and vacuum generator 153in FIG. 21A) via conduit 163, whereby the vacuum unit 168 provides acontrollable vacuum level to handpiece 40 for aspirating tissue receivedin inner cannula lumen 78. Vacuum unit 168 is electrically connected toa vacuum control unit 166 via a number, P, of signal paths 169 wherein Pmay be any integer. The vacuum control unit 166 is, in turn, connectedto a number of outputs of MCU 158 via an equal number, L, of signalpaths 167, wherein L may be any integer. A vacuum sensor 164, which maybe a temperature compensated solid-state pressure sensor, may bepositioned within the conduit 151 and electrically connected to a vacuumfeedback (VF) input of MCU 158 via signal path 165. Alternatively, thevacuum sensor 165 may be disposed within hand piece 42 or within thevacuum unit 168 itself.

In operation, the MCU 158 is responsive to a vacuum command signal,preferably provided by a corresponding control mechanism associated withcontrol panel 132, foot pedal 144, or an equivalent control mechanism,to provide one or more corresponding vacuum control signals to vacuumcontrol unit 166 along signal paths 167. The vacuum control unit 166, inturn, is responsive to the one or more vacuum control signals toactivate the vacuum unit 168 to thereby provide tissue cutting device 40with a desired level of vacuum. The actual vacuum level provided totissue cutting device 40 is sensed by vacuum sensor 164, which providesa corresponding vacuum feedback signal to the vacuum feedback input VFof MCU 158. The MCU 158 is then operable to compare the vacuum feedbacksignal with the vacuum command signal and correspondingly adjust the oneor more vacuum control signals to achieve the desired vacuum levelwithin tissue cutting device 40. Such closed-loop feedback techniquesare well known in the control systems art.

In one alternative embodiment, the MCU 158 can be replaced by individualmicroprocessors controlling the input and output for controlling theoperation of the motor 62 and the vacuum unit 168. In this alternativeembodiment, the motor control and vacuum control microprocessors can bePIC16CXX Series microcontrollers provided by Microchip, Inc. of ChandlerAriz. The motor control microcontrollers can receive input signals fromthe motor driver 172 (FIG. 23) and position sensor 174, as well as thefoot switch 144 and panel controls 132. Likewise, the vacuummicrocontroller can receive input signals from the vacuum sensor 164,the foot switch 144 and panel controls 138. Each microcontroller canprovide its own output to its driven component and have its own display,such as an LED display, indicative of its operational status. Moreover,the two units can communicate with each other to ensure clean cutting byproper timing of the cutting and aspiration functions.

Referring now to FIG. 23, one exemplary embodiment of the motor controlunit 160 is shown in greater detail. The motor control unit 160 in oneembodiment includes a pulse width modulation (PWM) generator circuit 170having a motor speed input connected to one of the MCU outputs 161 ₁. Ifmotor speed control is provided, the output 161 ₁ can provide a variablevoltage signal indicative of a desired motor speed and based upon theposition of a throttle, foot pedal, or other actuator. In certainembodiments, an additional input is connected to another one of the MCUoutputs 161 ₂. The signal at this output 161 ₂ can be a motor slowdownsignal as described below. Alternatively, the output 161 ₂ canconstitute a braking signal used in connection with a current feedbackmotor controller. As a further alternative, the slowdown command may becommunicated via the motor speed command itself, rather than through aseparate signal 161 ₂. In this instance, the output 161 ₂ may not berequired.

In the illustrated embodiment, the PWM is disposed within the motorcontrol unit 160. Alternatively, the PWM can be integrated into the MCU158, or into the separate motor control microprocessor discussed above.In embodiments that include motor speed control, the motor speed inputreceives a motor speed signal from MCU 158 indicative of desiredoperational speed of the motor 62. The slowdown input can receive aspeed adjustment signal from the MCU 158 based on an actual motor speedsignal provided by a motor sensor associated with the motor 62.

A motor driver circuit 172 is electrically connected to PWM generatorcircuit 170 via signal path 173 and receives a PWM drive signaltherefrom, which is a pulse width modulated signal indicative of desiredmotor speed. The motor driver circuit 172 provides a motor drive signal(MD) to motor 62 via signal path 175. While the disclosed embodimentcontemplates digital control of the motor using the PWM generatorcircuit 170, alternative embodiments can utilize closed loop feedbackanalog circuits, particularly where slower cutting speeds arecontemplated.

The motor drive signal includes a motor stop input that is connected toanother one of the MCU outputs 161 ₁. In accordance with one aspect ofthe present disclosure, MCU 158 provides a motor stop signal on signalpath 161 ₃, based on a motor deactivation command provided by footswitch 144 or panel control 138 and also based on a motor stopidentification signal provided by sensor 174, to stop the inner cannula76 in a desired position, as will be more fully described hereinafter.In certain embodiments, only the motor stop signal is utilized tocommand the motor to stop at the predetermined position. In thesecertain embodiments, the motor slowdown signal on path 161 ₂ can beeliminated, or the input on path 161 ₂ can be used for other controlsignals to the motor control circuit.

As mentioned previously, when tissue cutting device 40 is deactivated,inner cannula 76 may come to rest partially disposed within outercannula opening 49. Referring to FIGS. 25-27, three different stoppositions of inner cannula 76 are shown. FIG. 27 shows that innercannula 76 can be stopped in a position in which a portion of the tissueT is trapped between the outer cannula opening 49 and the inner cannuladistal end 79. Efforts at withdrawing outer cannula 44 from the surgicalsite may accordingly result in tearing of the tissue portion T′ awayfrom the surrounding tissue base T. Surgeons encountering such trappingwould typically be required to re-activate tissue cutting device 40 torelease the tissue portion T′ from the surrounding tissue base T. Toprevent such tissue trapping from occurring, deactivation of the motor62 is controlled in such a manner that the inner cannula distal end 79is positioned remotely from the outer cannula opening 49 when innercannula 76 stops reciprocating. However, in certain methods of use,device 40 is used as an aspiration wand. In those methods, the stopposition of inner cannula distal end 79 may be adjusted to differentlocations within outer cannula opening 49 in order to adjust the levelof aspiration supplied to a region of the anatomy proximate outercannula opening 49. For example, stop positions may be selected thatlimit the percent open area of outer cannula opening 49 to 25%, 50%, or75% of the total area of opening 49.

Referring again to FIGS. 23 and 24, controlled deactivation of the motor62 will now be described in detail. When it is desired to deactivatetissue cutting device 40, a motor stop command is provided such as viafoot switch 144 or a panel control 138. In one embodiment, MCU 158 isresponsive to the motor stop command to provide a slowdown signal to thePWM generator via signal path 161 ₂ which slows the action of motor 62.Preferably, the slowdown signal corresponds to a predefined signal leveloperable to drive the motor 62 at a motor speed below a motor speedthreshold level. Since motor 62 is a brushed DC motor, it has arotational resistance or resistive torque associated therewith asdescribed above. In addition, in some cases friction between the innercannula 76 and outer cannula 44 will increase the rotational resistance.Due to this combined rotational resistance, operation of the motor 62will cease very rapidly or nearly instantly if the motor drive signal onsignal path 142 is disabled while driving motor 62 below the motor speedthreshold. Accordingly, when device 40 is used to cut tissue, alignmentof position indicators 176 a or 176 b with sensor 174 preferablycorresponds to a position of the tissue cutting device 40 at which thereis no danger of trapping tissue between inner cannula distal end 79 andthe outer cannula opening 49, and sensor 174 is operable to produce themotor stop identification signal when so aligned with indicator 176 a or176 b.

In one embodiment, MCU 158 is operable to produce a motor stop signal onsignal path 161 ₃ when sensor 174 detects alignment of positionindicators 176 a or 176 b therewith after one passage thereby ofindicator 176 a or 176 b since producing the slowdown signal on signalpath 161 ₂. Allowing one passage of indicator 176 a or 176 b by sensor174 after issuing the slowdown signal ensures that the rotational speedof motor 62 is at or below the motor speed threshold when subsequentlyissuing the motor stop command, regardless of the position of indicator176 a or 176 b relative to sensor 174 when the slowdown command wasissued. After one passage of indicator 176 a or 176 b by sensor 174since issuing the slowdown signal, MCU 158 is responsive to the signalprovided by sensor 174 indicative of alignment of indicator 176 a or 176b therewith, to produce the motor stop signal on signal path 161 ₃. Themotor driver 172 is responsive to the motor stop signal to produce amotor disable signal on signal path 175. Due to the inherent rotationalresistance, motor 62 is responsive to the motor disable signal toimmediately cease operation thereof with indicator 176 a or 176 bsubstantially aligned with sensor 174, and with the inner cannula 76accordingly positioned so as not to trap tissue between inner cannuladistal end 79 and the outer cannula opening 44.

As mentioned above, in one exemplary embodiment, the inner cannula stopposition is user adjustable, such as by adjusting a panel control 138 onconsole 134. In accordance with the embodiment, it is contemplated thatthe stopped rotational position of cam 64, and therefore the innercannula distal end 79, may be instead aligned with a predetermineddifferential distance between the indicator 176 a/176 b and the sensor174. The braking characteristics of the inner cannula 76 and motor 62can be ascertained and the stopping distance determined so that thispredetermined differential distance can be calibrated accordingly.However, in a preferred embodiment, when inner cannula 76 comes to rest,the distal end 79 is located proximally of the outer cannula opening 44by a predetermined distance, as shown in FIG. 26.

A method of using device 40 to perform a tissue cutting procedure willnow be described in the context of a neurosurgical procedure involvingthe cutting of a neurological target tissue. In one example, the targettissue is brain tissue, and in another example the target tissue isspinal tissue, for example, the tissue of an intervertebral disk. Incertain exemplary methods, the tissue specimen being cut is a tumor or alesion.

In accordance with the method, it is first determined whether thecutting operation will be a debulking operation or a fine shavingoperation or a cutting operation that is somewhere in between adebulking and fine shaving operation. A surgical access path is thencreated to the tissue sample of interest. In one embodiment, thesurgical path is created and/or the target tissue is accessed using an“open” procedure in which the target tissue is open to the atmosphere(e.g., a full open craniotomy). In another embodiment, the surgical pathis created and/or the target tissue is accessed using a “closed”procedure in which the target tissue is sealed from the atmosphere.

At this point, the distal end 79 of inner cannula 76 is locatedproximally of outer cannula opening 69 due to the use of an innercannula stop position control of the type described previously. Themaximum vacuum level to be applied to device 40 is then set using panelcontrols 138. Generally, higher vacuum levels will be used for debulkingprocedures than for fine shaving procedures as higher vacuum levels willtend to draw relatively larger sections of tissue into outer cannulaopening 49. In one embodiment, the panel control 138 is a knob onconsole 134 that is rotated to set the desired maximum vacuum level.

In one arrangement, device 40 is configured to be gripped with a singlehand during a tissue cutting procedure. Thus, the surgeon will grasphandpiece 42 in the fingers of one hand and insert outer cannula 44 to alocation proximate the target tissue. Depending on the hand and thesurgeon's orientation with respect to the target tissue, the surgeon maythen rotate dial 60 to rotate outer cannula 44 about its ownlongitudinal axis and orient outer cannula opening 49 immediatelyadjacent the target tissue. The rotation of outer cannula 44 with dial60 causes inner cannula 76 to rotate such that a fixed rotational orangular relationship is maintained between inner cannula 76 and outercannula 44. Once the opening is in the desired orientation, the motor 62is activated, for example, by beginning to depress pedal 144 from itsfully undepressed (open) position to a second partially depressedposition which causes motor control unit 160 to send a signal to motor62 on signal path 142. Motor 62 may also be activated by a panel control138. The rotation of motor 62 causes cam 64 to rotate, resulting in thereciprocation of cam follower 68 and cam transfer 72. The reciprocationof cam transfer 72 causes cannula transfer 74 to reciprocate, therebyreciprocating inner cannula 76 within outer cannula lumen 110.

Once motor 62 is activated, vacuum is supplied to inner cannula lumen78. In one embodiment, as the pedal 144 is further depressed (beyond theposition at which motor 62 is activated), vacuum generator 153 isactivated. The surgeon then adjusts the degree of depression of the footpedal 144 to obtain the desired level of vacuum by visualizing themovement of the target tissue relative to the outer cannula opening 49.In certain embodiments, the surgeon controls the vacuum level to obtaina desired amount of traction in the tissue surrounding the targettissue. If the surgeon desires to apply the previously set maximumvacuum level, he or she depresses pedal 144 to its fully depressedposition.

If desired, the surgeon may depress and partially release the pedal 144a number of times to manipulate the target tissue in a satisfactorymanner. Vacuum controller 166 is manipulable to adjust the setpoint ofvacuum generator 153 which is manipulable to adjust the inner cannulavacuum level along a continuum of levels below the pre-selected maximumlevel. In one embodiment, the extent of depression of foot pedal 144dictates the vacuum set point supplied to vacuum control unit 166 onsignal path 167, and therefore, the amount of vacuum provided by vacuumunit 168. Vacuum sensor 164 measures the vacuum supplied to tissuecollector 58 and feeds a signal back to main control unit 158 on signalpath 165. The measured vacuum is then compared to the set point appliedto vacuum control unit 166 via foot pedal 144, and the signaltransmitted to vacuum generator 153 is then adjusted to move themeasured vacuum value towards the set point. To obtain a vacuum levelequal to the maximum pre-set level, pedal 144 is completely depressed.Maximum vacuum levels of at least about 0 in Hg. are preferred, andmaximum vacuum levels of at least about 1 in Hg. are more preferred.Maximum vacuum levels of at least about 5 in Hg. are even morepreferred, and maximum vacuum levels of at least about 10 in Hg. arestill more preferred. Maximum vacuum levels of at least about 20 in. Hg.are yet more preferred, and vacuum levels of at least about 29 in. Hg.are most preferred.

Due to the resistance of the tissue drawn into outer cannula opening 49,cutting section 83 pivots about hinge 80 and toward outer cannulaopening 49 as inner cannula 76 travels in the distal direction. Theinner cannula cutting section 83 continues to pivot as it travels in thedistal direction, eventually compressing tissue within outer cannulaopening 49 and severing it. The severed tissue forms a continuum oftissue snippets 112 (FIG. 14) within inner cannula lumen 78. Due to thevacuum applied to tissue collector 58, snippets 112 are aspiratedthrough inner cannula lumen 78 in the proximal direction. Theyeventually exit inner cannula lumen 78 at inner cannula proximal end 77and enter tissue collector 58 (or fluid collection canister 192 if nocollector 58 is provided). Any fluids that are aspirated exit tissuecollector 58 and are trapped in fluid collection canister 192. Thesurgeon preferably severs tissue at a cutting rate of at least about1,000 cuts/minute. Cutting rates of at least about 1,200 cuts/minute aremore preferred, and cutting rates of at least about 1,500 cuts/minuteare even more preferred. Cutting rates of less than about 2,500cuts/minute are preferred. Cutting rates of less than about 2,000 aremore preferred, and cutting rates of less than about 1,800 cuts/minuteare even more preferred.

The surgeon may move device 40 around the target tissue until thedesired degree of cutting has been completed. Motor 62 is thendeactivated, for example, by completely releasing pedal 144 so itreturns to its fully undepressed (open) position. If an inner cannulastop position control is provided, inner cannula 76 preferably comes torest proximally of outer cannula opening 49, as shown in FIG. 26. Outercannula 44 is then removed from the surgical site. Tissue collector 58is then removed from upper housing 52 of handpiece 42, and the collectedtissue samples are either discarded or saved for subsequent analysis.Fluids collected in canister 192 are preferably discarded. If the remotetissue collector of FIG. 21A is used, tissue samples may be removed fromit without removing outer cannula 44 from the surgical site or otherwisedisturbing the surrounding tissue.

It will be appreciated that the tissue cutting devices and methodsdescribed herein have broad applications. The foregoing embodiments werechosen and described in order to illustrate principles of the methodsand apparatuses as well as some practical applications. The precedingdescription enables others skilled in the art to utilize methods andapparatuses in various embodiments and with various modifications as aresuited to the particular use contemplated. In accordance with theprovisions of the patent statutes, the principles and modes of operationof this invention have been explained and illustrated in exemplaryembodiments.

It is intended that the scope of the present methods and apparatuses bedefined by the following claims. However, it must be understood thatthis invention may be practiced otherwise than is specifically explainedand illustrated without departing from its spirit or scope. It should beunderstood by those skilled in the art that various alternatives to theembodiments described herein may be employed in practicing the claimswithout departing from the spirit and scope as defined in the followingclaims. The scope of the invention should be determined, not withreference to the above description, but should instead be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled. It is anticipated andintended that future developments will occur in the arts discussedherein, and that the disclosed systems and methods will be incorporatedinto such future examples. Furthermore, all terms used in the claims areintended to be given their broadest reasonable constructions and theirordinary meanings as understood by those skilled in the art unless anexplicit indication to the contrary is made herein. In particular, useof the singular articles such as “a,” “the,” “said,” etc. should be readto recite one or more of the indicated elements unless a claim recitesan explicit limitation to the contrary. It is intended that thefollowing claims define the scope of the invention and that the methodand apparatus within the scope of these claims and their equivalents becovered thereby. In sum, it should be understood that the invention iscapable of modification and variation and is limited only by thefollowing claims.

1. A tissue removal device, comprising: a handpiece; an outer cannulahaving an outer cannula lumen, a proximal end, a distal end, and anouter cannula opening adjacent the distal end, wherein the openingdefines a cutting edge for severing tissue; an inner cannula disposed inthe outer cannula lumen and reciprocable within the outer cannula lumen,the inner cannula having an inner cannula lumen, a proximal end, an opendistal end, a cutting edge at the distal end, a living hinge, a cuttingsection, and a body section, with the hinge being located between thecutting section and the body section, wherein the cutting section ispivotable when the inner cannula reciprocates within the outer cannulalumen; and a tissue collector in fluid communication with the innercannula lumen; wherein the inner cannula reciprocates within the outercannula lumen between a proximal position and a distal position at arate that is at least about 1000 reciprocations per minute for forming acontinuum of severed tissue delivered to the tissue collector.
 2. Thetissue removal device of claim 1, wherein the outer cannula opening hasa width that varies longitudinally along the outer cannula and receivedtissue is compressed between the outer cannula cutting edge and theinner cannula cutting edge.
 3. The tissue removal device of claim 1,wherein when the outer cannula opening is viewed in plan, the outercannula opening is generally in the shape of a square.
 4. The tissueremoval device of claim 1, wherein when the outer cannula opening isviewed in plan, the outer cannula opening is generally in the shape of atrapezoid.
 5. The tissue removal device of claim 1, wherein when theouter cannula opening is viewed in plan, the outer cannula opening isgenerally in the shape of the letter “D.”
 6. The tissue removal deviceof claim 1, further comprising a motor connected to a cam that isoperatively connected to the inner cannula, such that rotation of themotor causes the cam to rotate.
 7. The tissue removal device of claim 1,further comprising a motor connected to a cam follower, wherein the camfollower is connected to a cam, the cam is operatively connected to theinner cannula, and rotation of the motor causes the cam follower torotate.
 8. The tissue removal device of claim 6, wherein the cam has alength, a surface, a continuous groove defined in the surface, and thegroove has at least one pair of apexes, wherein the members of the atleast one pair of apexes are spaced apart from one another along thelength of the groove.
 9. The tissue removal device of claim 1, whereinthe motor has a rotating shaft that is substantially parallel to theinner cannula and spaced apart from the inner cannula.
 10. The tissueremoval device of claim 1, further comprising a tissue aspiration pathfrom the inner cannula distal end to the inner cannula proximal end. 11.The tissue removal device of claim 1, further comprising a vacuumgenerator in fluid communication with the inner cannula lumen.
 12. Thetissue removal device of claim 1, wherein the outer cannula is rotatablewith respect to the handpiece, and when the outer cannula is rotatedwith respect to the handpiece, the inner cannula rotates with respect tothe handpiece to maintain a fixed circumferential orientation betweenthe outer cannula and the inner cannula.
 13. The tissue device of claim1, wherein the tissue collector has a longitudinal axis, the innercannula has a longitudinal axis, and the tissue collector longitudinalaxis is substantially collinear with the inner cannula longitudinalaxis.
 14. A method of performing a neurosurgical procedure, comprising:providing a tissue removal device comprising: a handpiece, an outercannula having an outer cannula lumen, a proximal end, a distal end, andan outer cannula opening adjacent the distal end, wherein the openingdefines a cutting edge for severing tissue, an inner cannula disposed inthe outer cannula lumen and reciprocable within the outer cannula lumen,the inner cannula having an inner cannula lumen, a proximal end, an opendistal end, a cutting edge at the distal end, a living hinge, a cuttingsection, and a body section, with the hinge being located between thecutting section and the body section, wherein the cutting section ispivotable when the inner cannula reciprocates within the outer cannulalumen, and a tissue collector in fluid communication with the innercannula lumen; inserting the outer cannula into a patient proximate atarget tissue associated with the patient's neurological system; andreciprocating the inner cannula within the outer cannula lumen between aproximal position and a distal position, such that when the innercannula is in the proximal position, the target tissue is received inthe outer cannula opening, and when the inner cannula is in the distalposition, the cutting section pivots and the received target tissue issevered from surrounding tissue, wherein during the reciprocating stepthe inner cannula severs tissue at a rate that is at least about 1000cuts per minute and forms a continuum of severed tissue that isdelivered to the tissue collector.
 15. The method of claim 14, furthercomprising aspirating the severed tissue in the proximal direction alongthe inner cannula lumen.
 16. The method of claim 14, further comprisingrotating the outer cannula with respect to the handpiece to align theouter cannula opening with the target tissue.
 17. The method of claim16, wherein the step of rotating the outer cannula with respect to thehandpiece further comprises simultaneously rotating the inner cannulawith respect to the handpiece to maintain a fixed circumferentialorientation between the inner cannula and the outer cannula.
 18. Themethod of claim 14, wherein the target tissue is spinal tissue.
 19. Themethod of claim 14, wherein the target tissue is brain tissue.
 20. Themethod of claim 14, further comprising creating an opening in thepatient's anatomy, wherein the step of inserting the outer cannula intothe patient proximate the target tissue comprises inserting the outercannula into the opening.
 21. The method of claim 14, wherein the targettissue comprises a tumor.
 22. The method of claim 14, wherein the targettissue comprises a lesion.
 23. The method of claim 14, wherein themethod is an open surgical procedure.
 24. A tissue removal system,comprising: a tissue removal device comprising: a handpiece, an outercannula having an outer cannula lumen, a proximal end, a distal end, andan outer cannula opening adjacent the distal end, wherein the openingdefines a cutting edge for severing tissue, an inner cannula disposed inthe outer cannula lumen and reciprocable within the outer cannula lumen,the inner cannula having an inner cannula lumen, a proximal end, an opendistal end, a cutting edge at the distal end, a living hinge, a cuttingsection, and a body section, with the hinge being located between thecutting section and the body section, wherein the cutting section ispivotable when the inner cannula reciprocates within the outer cannulalumen, and a tissue collector in fluid communication with the innercannula lumen; and a vacuum generator in fluid communication with theinner cannula lumen, wherein the vacuum generator is operable tomaintain the inner cannula lumen at a plurality of different vacuumlevels for fine shaving and debulking.
 25. The tissue removal system ofclaim 24, wherein the vacuum generator is operable to maintain the innercannula lumen at vacuum level that is no greater than a preselectedmaximum vacuum level while allowing the vacuum level to be variablyoperated at less than the preselected vacuum level.
 26. The tissueremoval system of claim 25, further comprising a vacuum controlleroperatively connected to the vacuum generator, wherein the vacuumcontroller is manipulable to adjust the inner cannula vacuum level alonga continuum of vacuum levels that are less than the preselected maximumvacuum level.
 27. The tissue removal system of claim 26, wherein thevacuum controller comprises a foot pedal.
 28. The tissue removal systemof claim 27, wherein the foot pedal is depressible from a first positionto a second position, and when the footpedal is depressed to the secondposition, the inner cannula vacuum level is the preselected maximumvacuum level.
 29. The tissue removal system of claim 24, furthercomprising a tissue sample aspiration path from the inner cannula distalend to the inner cannula proximal end.
 30. The tissue removal system ofclaim 24, wherein the tissue collector is disposed between the innercannula lumen and the vacuum generator.
 31. A method of performing aneurosurgical procedure, comprising: providing a tissue removal systemcomprising a tissue removal device, wherein the tissue removal devicecomprises: a handpiece, an outer cannula having an outer cannula lumen,a proximal end, a distal end, and an outer cannula opening adjacent thedistal end, wherein the opening defines a cutting edge for severingtissue, an inner cannula disposed in the outer cannula lumen andreciprocable within the outer cannula lumen, the inner cannula having aninner cannula lumen, a proximal end, a distal end, a cutting edge at thedistal end, a living hinge, a cutting section, and a body section, withthe hinge being located between the cutting section and the bodysection, wherein the cutting section is pivotable when the inner cannulareciprocates within the outer cannula lumen, and a tissue collector influid communication with the inner cannula lumen; inserting the outercannula into a patient proximate a target tissue associated with thepatient's neurological system; reciprocating the inner cannula withinthe outer cannula lumen between a proximal position and a distalposition, such that when the inner cannula is in the proximal position,the target tissue is received in the outer cannula opening, and when theinner cannula is in the distal position, the cutting section pivots andthe received target tissue is severed from surrounding tissue; andadjusting an inner cannula lumen vacuum level to aspirate tissue samplesthrough the inner cannula lumen, wherein the inner cannula lumen vacuumlevel is less than a preselected maximum vacuum level.
 32. The method ofclaim 31, wherein the step of adjusting the inner cannula lumen vacuumlevel comprises varying the inner cannula vacuum level along a continuumof vacuum levels that are less than the preselected maximum vacuumlevel.
 33. The method of claim 31, wherein the tissue removal systemfurther comprises a vacuum generator in fluid communication with theinner cannula lumen and a vacuum controller operatively connected to thevacuum generator, and the step of adjusting the inner cannula lumenvacuum level comprises manipulating the vacuum controller.
 34. Themethod of claim 33, wherein the vacuum controller comprises adepressible foot pedal, and the step of adjusting the inner cannulalumen vacuum level comprises depressing the footpedal.
 35. The method ofclaim 31, wherein the step of reciprocating the inner cannula within theouter cannula between the proximal position and the distal positionfurther comprises reciprocating the inner cannula within the outercannula at a substantially constant rate of reciprocation, and thesubstantially constant rate of reciprocation is at least about 1000reciprocations per minute.
 36. The method of claim 31, wherein the stepof adjusting the inner cannula vacuum level comprises adjusting theinner cannula vacuum level within a range of from about 0 in Hg. toabout 29 in. Hg.
 37. The method of claim 31, further comprisingobserving a level of traction in tissue surrounding the target tissue,wherein the step of adjusting an inner cannula lumen vacuum levelcomprises adjusting the inner cannula lumen vacuum level to maintain adesired level of traction.
 38. The method of claim 31, furthercomprising observing tissue surrounding the target tissue, wherein thestep of adjusting an inner cannula lumen vacuum level comprisesadjusting the inner cannula lumen vacuum level to avoid the occurrenceof traction in the tissue surrounding the target tissue.
 39. A tissueremoval system, comprising: a handpiece; an outer cannula having anouter cannula lumen, a proximal end, a distal end, and an outer cannulaopening adjacent the distal end, wherein the opening defines a cuttingedge for severing tissue; an inner cannula disposed in the outer cannulalumen and reciprocable within the outer cannula lumen, the inner cannulahaving an inner cannula lumen, a proximal end, an open distal end, acutting edge at the distal end, a living hinge, a cutting section, and abody section, with the hinge being located between the cutting sectionand the body section, wherein the cutting section is pivotable when theinner cannula reciprocates within the outer cannula lumen; a tissuecollector in fluid communication with the inner cannula lumen; and avacuum generator in fluid communication with the inner cannula lumen,wherein the vacuum generator is operable to maintain the inner cannulalumen at a plurality of different vacuum levels for fine shaving anddebulking, wherein the inner cannula reciprocates within the outercannula lumen between a proximal position and a distal position at arate that is no less than about 1000 reciprocations per minute forforming a continuum of severed tissue delivered to the tissue collector.40. The tissue removal system of claim 39, wherein the outer cannulaopening has a width that varies longitudinally along the outer cannulaand received tissue is compressed between the outer cannula cutting edgeand the inner cannula cutting edge.
 41. The tissue removal system ofclaim 39, further comprising a motor connected to a cam that isoperatively connected to the inner cannula, such that rotation of themotor causes the cam to rotate.
 42. The tissue removal system of claim39, wherein the cam has a length, a surface, a continuous groove definedin the surface, and the groove has at least one pair of apexes, whereinthe members of the at least one pair of apexes are spaced apart from oneanother along the length of the groove.
 43. The tissue removal system ofclaim 39, wherein the motor has a rotating shaft that is substantiallyparallel to the inner cannula and spaced apart from the inner cannula.44. The tissue removal system of claim 39, further comprising a tissueaspiration path from the inner cannula distal end to the inner cannulaproximal end.
 45. The tissue removal system of claim 39, wherein theouter cannula is rotatable with respect to the handpiece, and when theouter cannula is rotated, the inner cannula rotates to maintain a fixedcircumferential orientation between the outer cannula and the innercannula.
 46. The tissue removal system of claim 39, wherein the tissuecollector has a longitudinal axis that is substantially collinear withthe longitudinal axis of the inner cannula.
 47. The tissue removalsystem of claim 39, wherein the handpiece, the inner cannula, and theouter cannula comprise a tissue removal device.
 48. The tissue removalsystem of claim 39, wherein the vacuum generator is operable to maintainthe inner cannula lumen at a vacuum level that is no greater than apreselected maximum vacuum level while allowing the vacuum level to bevariably operated at less than the preselected vacuum level.
 49. Thetissue removal system of claim 48, further comprising a vacuumcontroller operatively connected to the vacuum generator, wherein thevacuum controller is manipulable to adjust the inner cannula vacuumlevel along a continuum of vacuum levels that are less than thepreselected maximum vacuum level.
 50. The tissue removal system of claim49, wherein the vacuum controller is a foot pedal.
 51. The tissueremoval system of claim 50, wherein the foot pedal is depressible from afirst position to a second position, and when the footpedal is depressedto the second position, the inner cannula vacuum level is thepreselected maximum vacuum level.
 52. The tissue removal system of claim39, wherein the tissue collector is disposed between the inner cannulalumen and the vacuum generator.